Method for the production of compounds containing palladium(0)

ABSTRACT

The present invention relates to a process for preparing a palladium(0) compound, comprising the reaction of a palladium compound with one or more compounds of the general formula I, II or III in the presence of a base: 
                         Term-O—{[Si(R 16 )(CR 19 CR 17 R 18 )O] v [Si(R 20 ) 2 O] w }-Term   (III). 
The Palladium(0) compounds are suitable as homogeneous catalysts, as a precursor for preparing homogeneous catalysts, as a precursor for preparing homogeneous catalysts in situ or as a precursor for preparing heterogeneous catalysts.

The present invention relates to a process for preparing palladium(0)compounds.

In the form of its compounds, palladium finds use as a catalyst innumerous industrial processes.

More than 80% of the industrially produced chemicals are prepared bycatalytic processes. Catalytic processes are generally more economicallyviable and environmentally friendly than corresponding stoichiometricorganic reactions. For the attainment of high yields and selectivitiesin homogeneous catalytic processes, a wide range of ligand systems hasto be used, which in turn requires precursor metal compounds having awide range of uses. This makes clear the need for constant improvementin the catalyst systems and their preparation processes.

For these applications, one possibility is in particular palladiumcompounds which contain palladium in the 0 oxidation state. In general,palladium(0) compounds are stabilized by compounds which can provide afree electron pair for coordination. This free electron pair may beprovided, for example, by an unsaturated hydrocarbon or by heteroatomssuch as phosphorus or nitrogen. Stably storable compounds arecommercially obtainable principally only in solid form.

However, compounds which are in liquid form are desired in catalysis.This greatly eases their usability. Often, solid compounds are dissolvedin a solvent for this purpose, but solutions of solid Pd(0) compoundsare usually unstable and have to be used immediately.

In homogeneous catalysis applications, the precursors used arepreferably compounds which can be mixed in a simple manner with ligands,for example different phosphines, so as to be able to prepare a widerange of catalysis systems. This is realized, for example, in the caseof the Pd(0) compounds stabilized with unsaturated hydrocarbon ligands.

Numerous Pd(0) complexes with unsaturated compounds in the ligandssphere are known and are described, for example, in Wilkinson, Abel“Comprehensive Organometallic Chemistry”, Vol. 6, p. 243ff “Complexes ofPalladium(0)”.

Pd(0) compounds stabilized by unsaturated hydrocarbons may bedifferentiated according to the ligands into complexes stabilized bymonodentate and by multidentate (chelating) ligands. An example of aPd(0) complex stabilized by monodentate hydrocarbon ligands isPd(ethylene)₃, which decomposes at room temperature and under air.

Stabler Pd(0) compounds are obtained by chelating, for examplebidentate, unsaturated hydrocarbon ligands such as dienes. Dienes areclassified according to the separation of the two diene functions into1,4-diene ligands, 1,5-diene ligands, 1,6-diene ligands, 1,7-dieneligands, etc.

1,4-Diene-stabilized palladium(0) finds wide use as a ligand, forexample, in the form of 1,5-diphenyl-1,4-pentadien-3-one (dba). Onedescription of the synthesis is given by M. F. Rettig et al. in Inorg.Synth., 1990, 28. The product is isolated from the synthesis solution asa sparingly soluble precipitate. The solid is substantially air-stable,but solutions in organic solvents of these compounds decompose withinhours (STREM catalogue: “Chemicals for research”, Catalogue No. 19,2001-2003).

The use of this complex type as a precursor in homogeneous catalysis isdescribed, for example, in U.S. Pat. No. 6,316,380. In EP-A-508 264,Pd(dba)₂ substituted by sulphoalkyl groups is used as homogeneouscatalyst in C—C coupling.

A known example of Pd(0) stabilized by 1,5-diene ligand is Pd(COD)₂.This is synthesized in DE-A-25 55 374 from Pd(COD)Cl₂ in the presence ofan organometallic compound, for example Li₂(COT)(COT=cyclooctatraene),sodium naphthalide or organoaluminium compounds, in solvents having noactive protons. The above patent application also describes thesynthesis of Pd(C₂H₄)₃ from Pd(COD)₂. Pd(COD)₂ is an unstable solidwhich decomposes within hours under atmospheric conditions. Thisproperty makes this compound industrially utilizable only to a limitedextent.

J. Krause, G. Cestaric, K.-J. Haack, K. Seevogel, W. Storm, K. R.Porschke (J. Am. Chem. Soc. 1999, 121, 9807-9823 and Chem. Commun. 1998,12, 1291) describe the synthesis of molecularly definedhepta-1,6-diene-, diallyl ether- andtetramethyldivinyldisiloxane-palladium(0), which are examples of Pd(0)stabilized by 1,6-diene ligands. The synthesis follows substantially theroute described for Pd(COD)₂. Oxygen-free solvents have to be used forthe synthesis and the materials have decomposition temperatures close toroom temperature.

For application in homogeneous catalysis, 1,6-diene-Pd(0)-phosphine and-carbene complexes have been identified. These compounds exhibit highactivities in the industrially used Heck reaction and the Suzuki C—Ccoupling reaction, and are described by M. G. Andreu, A. Zapf, M. Bellerin Chem. Comm., 2000, 245 and in DE-A-100 62 577.

In the prior art, 1,4-diene-stabilized Pd(0) compounds are usedindustrially. These exhibit sufficient stability, but solutions of thesecompounds are not storage-stable. 1,5- and 1,6-diene-stabilized Pd(0)compounds are distinctly less stable than the 1,4-diene-stabilized Pd(0)compounds. In all diene-stabilized Pd(0) compounds, it is typicallynecessary to work under inert gas and with dried solvents having noactive protons in order to isolate molecularly defined Pd₂(diene)₃ orPd(diene)₂ compounds. In addition, highly sensitive organolithiumcompounds which pose potential health risks are used in the synthesis,which makes industrial-scale utilization costly and inconvenient. Forthis reason, these compound classes have not been used industrially on alarge scale to date.

It is therefore an object of the present invention to provide a novelinexpensive process for preparing palladium(0) compounds. Solutions ofthese compounds should be substantially stable thermally and towardatmospheric conditions. This enables access to economically viable,versatile, novel precursors for applications in homogeneous catalysis,heterogeneous catalysis and complex chemistry.

In particular, the invention relates to a process for preparing aPalladium(0) compound, comprising reaction of a palladium compound withone or more compounds of the general formula (I) in the presence of abase:

in which:

each A is independently a CR⁷R⁸ radical where one of the A radicals maybe oxygen, sulphur, an NR⁹ group or an SiR¹⁰R¹¹ group, or where the Aradicals may be a constituent of a 5- to 20-membered ring system,

x is an integer from 2 to 4, and

each R¹ to R¹¹ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is a hydrogen atom, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R² and R³ and/or R⁵ and R⁶together with the carbon atoms bonded thereto may be a constituent of a5- to 7-membered, optionally heteroatom-containing ring.

In a further embodiment, the invention relates to a process forpreparing a Palladium(0) compound, comprising reaction of a palladiumcompound with one or more compounds of the general formula II in thepresence of a base:

in which:

n is an integer from 3 to 20,

each R³ to R¹⁵ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is hydrogen, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R¹³ and R¹⁴ together with thecarbon atoms bonded thereto may be a constituent of a 5- to 7-membered,optionally heteroatom-containing ring, and

each R¹² is independently selected from hydrogen, a hydroxyl group, asubstituted or unsubstituted C₁₋₁₀-alkyl radical (in particular anunsubstituted or halogenated C₁-₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted; inparticular an unsubstituted or halogenated-O—C₁-₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical, where the substituents are asdefined for R¹³ and R¹⁵.

In yet a further embodiment, the invention relates to a process forpreparing a Palladium(0) compound, comprising reaction of a palladiumcompound with one or more compounds of the general formula III in thepresence of a base:Term-O—{[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O]_(v)[Si(R²⁰)₂O]_(w)}-Term  (III)in which

v and w are each independently 0 or an integer of from 1 to 1000 and v+wis from 0 to 1000,

each R¹⁶ is independently selected from a hydrogen atom, a hydroxylgroup, a substituted or unsubstituted C₁₋₁₀-alkyl radical (in particularan unsubstituted or halogenated C₁-₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted; inparticular an unsubstituted or halogenated —O—C₁-₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical, where the substituents are asdefined for R¹⁷ and R¹⁹,

each R¹⁷ to R¹⁹ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is hydrogen, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R¹⁷ and R¹⁹ together with thecarbon atoms bonded thereto may be a constituent of a 5- to 7-membered,optionally heteroatom-containing ring,

each R²⁰ is independently selected from hydrogen, a hydroxyl group, asubstituted or unsubstituted C₁₋₁₀-alkyl radical (in particular anunsubstituted or halogenated C₁₋₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted inparticular an unsubstituted or halogenated —O—C₁₋₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical, or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical, where the substituents are asdefined for R¹⁷ and R¹⁹, and

each Term radical is independently (R¹⁶)₂(CR¹⁷R¹⁸CR¹⁹)Si— or (R¹⁶)₃Si—.

Surprisingly, the above-described processes, unlike the processes knownto date, can be carried out at temperatures above 0° C. In addition, thereaction does not have to be carried out with exclusion of air or withdried solvents.

In the palladium(0) compounds, palladium is present as palladium(0). Theoxidation state of palladium in the compounds can be determined by knownprocesses, for example by reacting with uncharged ligands (for examplephosphines), isolating and characterizing the resulting compound withNMR, or by concentrating the solution by evaporation and determining theoxidation state by means of XPS.

Palladium Compound

The palladium compound used as the starting compound is not particularlyrestricted. It may be used either in the form of solids or in the formof aqueous or hydrochloric acid solutions. Preference is given to usingpalladium compounds having palladium in the +2 or +4 oxidation state.Examples thereof are PdX₂, PdX₄, M₂PdX₄, M₂PdX₆, (NH₃)₂PdX₂ and[Pd(NH₃)₄]X₂, where M is a cation (e.g.: a hydrogen atom, an alkalimetal (in particular Na⁺ or K⁺) or NR*₄ ⁺ (R*=hydrogen, C₁₋₄alkyl)) andX is an anion (e.g.: halogen (in particular chlorine), NO₃ ⁻).Particularly preferred palladium compounds are PdCl₂, PdCl₄, Pd(NO₃)₂,[Pd(NH₃)₄]Cl₂, (NH₃)₂PdCl₂, H₂PdCl₄, H₂PdCl₆, Na₂PdCl₄, Na₂PdCl₆,K₂PdCl₄ and K₂PdCl₆.

Ligand of the General Formula I

The palladium compound is reacted with one or more compounds of thegeneral formula I

Each A is independently a CR⁷R⁸ radical where one of the A radicals maybe oxygen, sulphur, an NR⁹ group or an SiR¹⁰R¹¹ group, or where the Aradicals may be a constituent of a 5- to 20-membered ring system.

x is an integer of from 2 to 4.

Each R¹ to R¹¹ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is hydrogen, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R² and R³ and/or R⁵ and R⁶together with the carbon atoms bonded thereto may be a constituent of a5- to 7-membered, optionally heteroatom-containing ring.

Examples of heteroatom-containing rings are rings which derive from thefollowing structures: thiophenes, furans, pyrans, pyrroles and the like.Other rings are likewise possible.

In a preferred embodiment, R¹ to R⁶ are each independently hydrogenatoms, C₁₋₄-alkyl radicals or halogenated C₁₋₄-alkyl radicals; R¹ to R⁶are more preferably hydrogen atoms.

In a further preferred embodiment, R⁷ and R⁸ are preferably eachindependently hydrogen atoms, C₁₋₄-alkyl radicals or halogenatedC₁₋₄-alkyl radicals; R⁷ and R⁸ are more preferably hydrogen atoms.

In yet a further embodiment, R⁹ is preferably independently a hydrogenatom, a C₁₋₄-alkyl radical, a halogenated C₁₋₄-alkyl radical, a—C(O)—C₁₋₄ alkyl radical or a halogenated —C(O)—C₁₋₄ alkyl radical.

In a further embodiment, R¹⁰ and R¹¹ are each independently selectedfrom a hydroxyl group, a C₁₋₄ alkyl radical, an —O—C₁₋₄ alkyl radical, ahalogenated C₁₋₄-alkyl radical or a halogenated —O—C₁₋₄-alkyl radical.R¹⁰ and R¹¹ are more preferably each independently a C₁₋₄-alkyl radicalor a halogenated C₁₋₄-alkyl radical.

R is preferably a hydrogen atom, a C₁₋₄-alkyl radical or a halogenatedC₁₋₄-alkyl radical.

Halogens refer to fluorine, chlorine, bromine and iodine, preferablyfluorine and chlorine. The radicals substituted by them may be mono- orpolysubstituted, preferably perhalogenated.

The compounds of the formula I are preferably symmetrical.

In one embodiment, the -(A)_(x)-group is preferably a group of theformula —CH₂—X—CH₂— and —X— is selected from —O—, —S—, —SiR₂—, —NR— and—NC(O)R, where R is a hydrogen atom, a C₁₋₄-alkyl radical, a halogenatedC₁₋₄-alkyl radical, an O—C₁₋₄-alkyl radical, a halogenated O—C₁₋₄-alkylradical, a C₁₋₄-alkenyl radical or an optionally heteroatom-containingC₅₋₆-aryl radical.

Illustrative examples of compounds of the general formula I are1,5-hexadiene, 1,6-heptadiene and 1,7-octadiene. Further compounds whichmay serve as illustration are diallyl ether, diallylamine,diallyl-methylamine, diallylethylamine, N-acetyldiallylamine, diallylsulphide, diallylsilane, diallyldimethylsilane, difurfuryl ether,difurfurylamine, bis(thiophen-2-yl-methyl)amine, difurfuryl sulphide and1,3-divinyl-benzene.

Ligand of the General Formula II

The present invention further provides a process for preparing apalladium(0) compound, comprising reaction of a palladium compound withone or more compounds of the general formula II in the presence of abase:

n is an integer from 3 to 20; n is preferably an integer from 3 to 6.

Each R¹³ to R¹⁵ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is hydrogen, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R¹³ and R¹⁴ together with thecarbon atoms bonded thereto may be a constituent of a 5- to 7-membered,optionally heteroatom-containing ring.

Examples of heteroatom-containing rings are rings which derive from thefollowing structures: thiophenes, furans, pyrans, pyrroles and the like.Other rings are likewise possible.

In a preferred embodiment, R¹³ to R¹⁵ are each independently hydrogenatoms, C₁₋₄-alkyl radicals or halogenated C₁₋₄-alkyl radicals; R¹³ toR¹⁵ are more preferably hydrogen atoms.

Each R¹² is independently selected from hydrogen, a hydroxyl group, asubstituted or unsubstituted C₁₋₁₀-alkyl radical (in particular anunsubstituted or halogenated C₁₋₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted; inparticular an unsubstituted or halogenated —O—C₁₋₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical. The substituents are each asdefined for R¹³ to R¹⁵. Each R¹² is preferably selected independentlyfrom a hydroxyl group, a C₁₋₄-alkyl radical, an —O—C₁₋₄-alkyl radical, ahalogenated C₁₋₄-alkyl radical or a halogenated —O—C₁₋₄-alkyl radical.Each R¹² is more preferably each independently a C₁₋₄-alkyl radical or ahalogenated C₁₋₄-alkyl radical.

R is preferably a hydrogen atom, a C₁₋₄-alkyl radical or a halogenatedC₁₋₄-alkyl radical.

Halogens refer to fluorine, chlorine, bromine and iodine, preferablyfluorine and chlorine. The radicals substituted with them may be mono-or polysubstituted, preferably perhalogenated.

Ligand of the General Formula III

The present invention also provides a process for preparing apalladium(0) compound, comprising reaction of a palladium compound withone or more compounds of the general formula III in the presence of abase:Term-O—{[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O]_(v)[Si(R²⁰)₂O]_(w)}-Term  (III).

This formula encompasses both compounds in which the[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O] and [Si(R²⁰)₂O] units occur in blocks andcompounds in which individual [Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O] and [Si(R²⁰)₂O]units are distributed randomly in the chain. Mixed forms are likewisepossible.

v and w are each independently 0 or an integer from 1 to 1000 and v+w isfrom 0 to 1000. v and w are preferably each independently 0 or aninteger from 1 to 100 and v and w is from 0 to 100; more preferably vand w are each independently 0 or an integer from 1 to 20 and v+w isfrom 0 to 20.

Each R¹⁶ is independently selected from a hydrogen atom, a hydroxylgroup, a substituted or unsubstituted C₁₋₁₀-alkyl radical (in particularan unsubstituted or halogenated C₁₋₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted; inparticular an unsubstituted or halogenated —O—C₁₋₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical. The substituents are each asdefined for R¹⁷ and R¹⁹. Each R¹⁶ is preferably each independentlyselected from a hydroxyl group, a C₁₋₄-alkyl radical, an —O—C₁₋₄-alkylradical, a halogenated C₁₋₄-alkyl radical or a halogenated—O—C₁₋₄-alkyl-radical. Each R¹⁶ is more preferably each independently anC₁₋₄-alkyl radical or a halogenated C₁₋₄-alkyl radical.

Each R¹⁷ to R¹⁹ is independently selected from R, OR, halogen, CN, NO₂,NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃,Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H,PO(OR)₂, in which R is an hydrogen, a substituted or unsubstitutedC₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- orpolyunsaturated C₁₋₁₀-alkenyl radical, or a substituted orunsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, andthe substituents on the alkyl radical or the alkenyl radical areselected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ andhalogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical areselected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH,NH₂ and halogenated C₁₋₁₀-alkyl, where R¹⁷ and R¹⁹ together with thecarbon atoms bonded thereto may be a constituent of a 5- to 7-membered,optionally heteroatom-containing ring.

The examples of heteroatom-containing rings are rings which derive fromthe following structures: thiophenes, furans, pyrans, pyrroles and thelike. Other rings are likewise possible.

In a preferred embodiment, R¹⁷ to R¹⁹ are each independently hydrogenatoms, halogens, C₁₋₄-alkyl radicals or halogenated C₁₋₄-alkyl radicals;R¹⁷ to R¹⁹ are more preferably hydrogen atoms.

Each R²⁰ is independently selected from a hydrogen atom, a hydroxylgroup, a substituted or unsubstituted C₁₋₁₀-alkyl radical (in particularan unsubstituted or halogenated C₁₋₁₀-alkyl radical), an —O—C₁₋₁₀-alkylradical (where the alkyl radical may be substituted or unsubstituted; inparticular an unsubstituted or halogenated —O—C₁₋₁₀-alkyl radical), asubstituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenylradical, or a substituted or unsubstituted, optionallyheteroatom-containing C₅₋₁₀-aryl radical. The substituents are each asdefined for R¹⁷ and R¹⁹. Each R²⁰ is preferably independently selectedfrom a hydrogen atom, a hydroxyl group, a C₁₋₄-alkyl radical, an—O—C₁₋₄-alkyl radical, a halogenated C₁₋₄-alkyl radical or a halogenated—O—C₁₋₄-alkyl radical. Each R²⁰ is more preferably independently ahydrogen atom, a C₁₋₄-alkyl radical or a halogenated C₁₋₄-alkyl radical.

Each Term radical is independently (R¹⁶)₂(CR¹⁷R¹⁸CR¹⁹)Si— or (R¹⁶)₃Si—.The unsaturated radical is preferably (R¹⁶)₂(CR¹⁷R¹⁸CR¹⁹)Si—.

R is preferably a hydrogen atom, a C₁₋₄-alkyl radical or a halogenatedC₁₋₄-alkyl radical.

Halogens refer to fluorine, chlorine, bromine and iodine, preferablyfluorine and chlorine. The radicals substituted with them may be mono-or polysubstituted, preferably perhalogenated.

In a preferred embodiment, w is 0. In this case, the compounds of thegeneral formula (III) have the following form:Term-O—[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O]_(v)-Termwhere R¹⁶ to R¹⁹, Term and v are each as defined above.

Illustrative examples of compounds of the general formulae II and IIIare divinyldisiloxane, 1,1,3,3-tetramethyl-1,3-divinyldisiloxane,1,1,3,3-tetramethyl-1,3-dithien-2-yldisiloxane,1,1,3,3-tetramethoxy-1,3-divinyldisiloxane,1,3-dimethyl-1,3-divinyldisiloxane-diol,1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetra-siloxane and1,3,5-trimethyl-1,3,5-trivinylcyclo-trisiloxane. Particular preferenceis given to 1,1,3,3-tetramethyl-1,3-divinyldisiloxane,1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane and1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane.

It goes without saying that the palladium compound can be reacted withmixtures of the compounds of the general formula I, II and III. In thereaction of the palladium compound with one or more of the compounds ofthe general formula I, II and III, preference is given to no furtherligands in addition to the compounds of the general formula I, II andIII during the reaction.

Base

The palladium compound is reacted with one or more compounds of thegeneral formula I, II or III in the presence of a base. In the contextof the invention, “base” refers to inorganic and organic (preferablyinorganic) bases, but not organometallic bases. The bases should notdecompose in water. Suitable bases are, for example, salts of Bronstedacids. Preference is given to using carbonates, hydrogencarbonates,acetates, formates, ascorbates, oxalates and hydroxides. These may beused in the form of their ammonium (NR₄ ⁺ where R═H or C₁₋₄-alkyl),alkali metal (for example sodium or potassium) and alkaline earth metalsalts.

Solvent

The components are reacted typically in a solvent. The solvents are notparticularly restricted. Examples of possible solvents are water,alcohols, hydrocarbons (e.g. aromatic hydrocarbons such as benzene andtoluene or aliphatic hydrocarbons such as pentane, hexane and heptane),open-chain or cyclic ethers, amides and esters. However, preference isgiven to water, C₁₋₆ alcohols (e.g. C₁₋₄ alcohols such as methanol,ethanol, propanol and butanol) and C₂₋₆ ethers as solvents. Mixtures ofthese solvents may likewise be used.

Reducing Agent

In order to accelerate the reaction or achieve very substantialconversion, the reaction may optionally be effected in the presence of areducing agent. Suitable reducing agents are those which, compared tothe palladium compound used, have a lower redox potential under theselected reaction conditions. For example, formic acid and saltsthereof, oxalic acid and salts thereof, hydrazine, glucose, ascorbicacid or formaldehyde can be used. Instead of using a separate reducingagent, it is likewise possible to use a solvent which has reducingproperties.

Performance of the Process

In one possible embodiment of the process according to the invention,the palladium compound and the compound of the general formula I, II orIII is preferably dissolved in a solvent and the base is suspended inthe solution. The reactants are reacted with one another. To this end,the reactants are introduced into a reactor and stirred. The reactionmay be effected at a temperature of −78° C. to +200° C., preferably of−10° C. to +100° C. and more preferably of 0° C. to +50° C. The pressureis generally 0.1 mbar to 100 bar, preferably 0.2 to 2 bar. Particularpreference is given to ambient pressure ±0.2 bar. The reaction time iscommonly 5 minutes to 1 week, preferably 5 minutes to 24 hours, morepreferably 30 minutes to 24 hours. As mentioned above, it is notnecessary to work with exclusion of air, which is particularlyadvantageous for the industrial-scale application of the processaccording to the invention.

Based on 1 equivalent of palladium in the form of the compound used, 1to 100 equivalents, preferably 3 to 100 equivalents, more preferably 8to 20 equivalents, of the compound of the general formula I, II or IIIare used. The base is used in an amount of 1 to 100 equivalentspreferably of 2 to 100 equivalents, more preferably of 2.5 to 10equivalents, based on 1 equivalent of palladium. If present, thereducing agent may be added in an amount of 1 to 100 equivalents basedon 1 equivalent of palladium. Instead of using a separate reducingagent, it is likewise possible to use a solvent which has reducingproperties. In this case, the amount of the reducing agent (solvent) isnot particularly restricted, but rather it can be used in any excessbased on 1 equivalent of palladium.

The palladium(0) compounds may be used as such after the reaction.However, it is possible to purify and/or to concentrate the solutionsbefore use. Useful purification steps are, for example, thefiltering-off of by-products, the drying of the solution (for exampleover molecular sieves or MgSO₄) or the purification over activatedcarbon. The solution may be concentrated, for example, by distillation.

The palladium(0) compounds prepared by the process according to theinvention are also storage-stable and can be handled under air,generally at temperatures up to 30° C., in some cases up to 60° C. andhigher. They typically have a metal content of 0.01% by weight to 40% byweight, preferably of 0.01% by weight to 30% by weight, more preferablyof 0.01% by weight to 20% by weight, and a total halogen content of notmore than 5% by weight, preferably not more than 2% by weight, morepreferably not more than 1% by weight.

The palladium(0) compounds may, either alone or as a mixture, be used asa precursor for catalysts for organic chemistry reactions, by mixingthem with a ligand, for example phosphines, phosphites, phosphonites,amines, alkenes, thioethers, alkynes or carbenes, each of which may alsobe generated in situ. This mixture may be used directly as a catalyst,or the resulting complex may be obtained in substance by customaryprocesses from the mixture.

The inventive palladium(0) compounds may, either alone or as a mixture,also be used directly without using additional ligands as a catalystprecursor in organic chemistry reactions.

The examples which follow are intended to further illustrate theinvention. However, the invention is not restricted to theseillustrative embodiments, but rather is defined by the claims.

EXAMPLES General Method for the Synthesis of Palladium(0) Compounds

One equivalent of sodium tetrachloropalladate was dissolved in methanol.To this solution were added 8 equivalents of sodium hydrogencarbonateand 10 equivalents of a compound of the general formula I. The solutionwas stirred for 4 hours. The methanol was distilled off and the residuestirred over a desiccant and activated carbon. The solids were filteredoff and the filtrate was concentrated by distillation. Depending on thedistillation conditions, stable palladium solutions having palladiumcontents of 0.01 to 20% by weight were obtained.

According to this method, reaction mixtures were prepared with the di-to tetraenes specified in Table 1.

The palladium and chlorine content was determined by means of ICP-OESafter digestion or by Wickbold combustion.

Method for the Synthesis of Phosphine-Diene-Pd(0) Complexes

One palladium equivalent of the palladium solution obtained from thereaction of 1,1,3,3-tetramethyl-1,3-divinyldisiloxane was admixed withone equivalent of a 5% by weight ethereal tricyclohexylphosphinesolution. The resulting precipitate is filtered off and dried. Theproduct was identified by means of ¹H, ³¹P and ¹³C NMR spectroscopy astricyclohexylphosphine-(1,1,3,3-tetramethyl-1,3-divinyldisiloxane)-Pd(0)complex.

TABLE 1 Pd Cl Yield content content Diene component [%] [%] [%] Ex. 1 817.9 0.11 Diallyl ether Ex. 2 69 3.3 0.5 1,5-Hexadiene Ex. 3 78 5.2 0.111,7-Octadiene Ex. 4 84 8.0 0.1 Diallylamine Ex. 5 87 8.0 0.09Diallylmethylamine Ex. 6 91 18.6 0.02 1,1,3,3-Tetramethyl-1,3-divinyl-disiloxane Ex. 7 94 2.3 0.03 1,3,5,7-Tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane Ex. 8 91 10.0 0.021,3,5,-Trimethyl-1,3,5-trivinylcyclo- trisiloxane

1. Process for preparing a Palladium(0) compound, comprising reaction of a palladium compound with one or more compounds of the general formula I in the presence of a base:

in which: each A is independently a CR⁷R⁸-radical where one of the A radicals may be oxygen, sulphur, an NR⁹ group or an SiR¹⁰R¹¹ group, or where the A radicals may be a constituent of a 5- to 20-membered ring system, x is an integer from 2 to 4, and each R¹ to R¹¹ is independently selected from R, OR, halogen, CN, NO₂, NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃, Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H, PO(OR)₂, in which R is a hydrogen atom, a substituted or unsubstituted C₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical, or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, and the substituents on the alkyl radical or the alkenyl radical are selected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical are selected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, where R² and R³ and/or R⁵ and R⁶ together with the carbon atoms bonded thereto may be a constituent of a 5- to 7-membered, optionally heteroatom-containing ring.
 2. Process according to claim 1, wherein x is
 3. 3. Process according to claim 1, wherein R¹ to R⁶ are each hydrogen atoms.
 4. Process according to claim 1, wherein -(A)_(x)- is a group of the formula —CH₂—X—CH₂— and —X— is selected from —O—, —S—, —SiR₂—, —NR— and —NC(O)R, and R is hydrogen, a C₁₋₄-alkyl radical or a halogenated C₁₋₄-alkyl.
 5. Process according to claim 1, wherein the compound of the general formula I is selected from 1,5-hexadiene, 1,6-heptadiene and 1,7-octadiene.
 6. Process according to claim 1, wherein the compound of the general formula I is selected from diallyl ether, diallylamine, diallylmethylamine, diallylethylamine, N-acetyldiallylamine, diallyl sulphide, diallylsilane, diallyldimethylsilane, difurfuryl ether, difurfurylamine, bis(thiophen-2-ylmethyl)amine, difurfuryl sulphide and 1,3-divinylbenzene.
 7. Process for preparing a Palladium(0) compound, comprising reaction of a palladium compound with one or more compounds of the general formula II in the presence of a base:

in which: n is an integer from 3 to 20, each R¹³ to R¹⁵ is independently selected from R, OR, halogen, CN, NO₂, NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃, Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H, PO(OR)₂, in which R is hydrogen, a substituted or unsubstituted C₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical, or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, and the substituents on the alkyl radical or the alkenyl radical are selected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical are selected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, where R¹³ and R¹⁴ together with the carbon atoms bonded thereto may be a constituent of a 5- to 7-membered, optionally heteroatom-containing ring, and each R¹² is independently selected from hydrogen, a hydroxyl group, a substituted or unsubstituted C₁₋₁₀-alkyl radical, an —O—C₁₋₁₀-alkyl radical (where the alkyl radical may be substituted or unsubstituted), a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, where the substituents are as defined for R¹³ and R¹⁵.
 8. Process according to claim 7, wherein n is an integer from 3 to 6 and each R¹² is independently a C₁₋₄-alkyl radical or a halogenated C₁₋₄-alkyl radical.
 9. Process for preparing a Palladium(0) compound, comprising reaction of a palladium compound with one or more compounds of the general formula III in the presence of a base: Term-O—{[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O]_(v)[Si(R²⁰)₂O]_(w)}-Term  (III) in which v and w are each independently 0 or an integer of from 1 to 1000 and v+w is from 0 to 1000, each R¹⁶ is independently selected from hydrogen, a hydroxyl group, a substituted or unsubstituted C₁₋₁₀-alkyl radical, an —O—C₁₋₁₀-alkyl radical (where the alkyl radical may be substituted or unsubstituted), a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, where the substituents are as defined for R¹⁷ and R¹⁹, each R¹⁷ to R¹⁹ is independently selected from R, OR, halogen, CN, NO₂, NR₂, C(O)R, C(O)OR, OC(O)R, CONR₂, NHCO₂R, NHCOR, CH═CH—CO₂R, Si(R)₃, Si(OR)₃, SiR(OR)₂, SiR₂(OR), SO₃R, SO₂R, SOR, SR, PR₂, POR₂, PO₃H, PO(OR)₂, in which R is a hydrogen atom, a substituted or unsubstituted C₁₋₁₀-alkyl radical, a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical, or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, and the substituents on the alkyl radical or the alkenyl radical are selected from halogen, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, and the substituents on the aryl radical are selected from halogen, C₁₋₁₀-alkyl, O—C₁₋₁₀-alkyl, phenyl, O-phenyl, OH, NH₂ and halogenated C₁₋₁₀-alkyl, where R¹⁷ and R¹⁹ together with the carbon atoms bonded thereto may be a constituent of a 5- to 7-membered, optionally heteroatom-containing ring, each R²⁰ is independently selected from hydrogen, a hydroxyl group, a substituted or unsubstituted C₁₋₁₀-alkyl radical, an —O—C₁₋₁₀-alkyl radical (where the alkyl radical may be substituted or unsubstituted), a substituted or unsubstituted, mono- or polyunsaturated C₁₋₁₀-alkenyl radical, or a substituted or unsubstituted, optionally heteroatom-containing C₅₋₁₀-aryl radical, where the substituents are as defined for R¹⁷ and R¹⁹, and each Term is independently (R¹⁶)₂(CR¹⁷R¹⁸CR¹⁹)Si— or (R¹⁶)₃Si—.
 10. Process according to claim 9, wherein the compound of the general formula (III) has the general formula: Term-O—[Si(R¹⁶)(CR¹⁹CR¹⁷R¹⁸)O]_(v)-Term where R¹⁶ to R¹⁹, Term and v are each as defined in claim
 9. 11. Process according to claim 7, wherein the compound of the general formula II or III is selected from divinyldisiloxane, 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, 1,1,3,3-tetramethyl-1,3-dithien-2-yldisiloxane, 1,1,3,3-tetramethoxy-1,3-divinyldisiloxane, 1,3-dimethyl-1,3-divinyldisiloxanediol, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane.
 12. Process according to claim 7, wherein the compound of the general formula II or III is selected from 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane and 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane.
 13. Process according to claim 1, wherein the palladium compound is selected from PdX₂, PdX₄, M₂PdX₄, M₂PdX₆, (NH₃)₂PdX₂ and [Pd(NH₃)₄]X₂, where M is a hydrogen atom, an alkali metal or NR*₄ ⁺ (R*=hydrogen, C₁₋₄-alkyl) and X is a halogen or NO₃ ⁻.
 14. Process according to claim 13, wherein X is chlorine.
 15. Process according to claim 1, wherein the reaction is effected in the presence of a solvent or solvent mixture.
 16. Process according to claim 15, wherein the solvent is selected from water, C₁₋₆-alcohols and C₂₋₆-ethers and mixtures thereof.
 17. Process according to claim 1, wherein the base is selected from alkali metal salts, alkaline earth metal salts and ammonium salts (ammonium as NR₄ ⁺ where R═H or C₁₋₄-alkyl) of carbonates, hydrogencarbonates and hydroxides.
 18. Process according to claim 1, also comprising a purification step.
 19. Process according to claim 1, also comprising a concentration step.
 20. Process according to claim 1, wherein the reaction of the palladium compound with one or more compounds of the general formula I, II or III is carried out in the presence of one or more ligands other than the compound of the general formula I, II or III.
 21. Process according to claim 1, further comprising the reaction of the palladium compound with one or more ligands other than the compound of the general formula I, II or III.
 22. Palladium(0) compound obtainable by a process according to claim 7, wherein the compound of the general formula II is 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane. 